This invention relates to an exposure apparatus in which the exposing light used is short-wavelength ultraviolet light, especially, light emitted by a light source such as an excimer laser, a harmonic laser or a mercury lamp and having an emission spectral line that overlaps the absorption spectrum region of oxygen, to a semiconductor device manufacturing method that utilizes this exposure apparatus, and to a semiconductor device manufacturing plant in which this exposure apparatus is installed.
In lithography for manufacturing semiconductor devices, use is made of an exposure apparatus in which the image of a predetermined pattern that has been formed on a mask or reticle (referred to generically as a reticle below) is projected onto a photosensitive plate (referred to generically as a substrate below) such as a wafer or glass plate via a projection optics unit to thereby expose the substrate to the pattern. The line width of semiconductor devices is becoming increasingly small. In order to cope with this trend, lithographic processes now generally employ methods of shortening the wavelength of the exposing light emitted from the exposing light source.
An exposure apparatus in which a KrF excimer laser having a wavelength of 248 nm is used as the exposing light source has already been developed, and at present the development of an exposure apparatus in which a short-wavelength 193-nm ArF excimer laser is used as the exposing light source is in progress. An F2 excimer laser having a wavelength of 157 nm has become the focus of attention as a next-generation exposing light source.
In a conventional exposure apparatus using a mercury lamp or KrF excimer laser which emits g or i lines, the emission spectral line of the exposing light emitted from these exposing light sources does not overlap the absorption spectrum region of oxygen and therefore the problems of a decline in light utilization efficiency (transmittance), which is brought about by absorption of light by oxygen, and evolution of ozone do not occur. Accordingly, the conventional exposure apparatus basically makes it possible to perform exposure in the atmosphere.
With an exposure apparatus that uses an F2 excimer laser, on the other hand, the emission spectral line of the F2 excimer laser beam overlaps the absorption spectrum region of oxygen. The serious problems that result are the aforementioned decline in transmittance ascribed to absorption of light by oxygen and the evolution of ozone. For example, the transmittance of an F2 excimer laser in the atmosphere is actually on the order of 0.1%/mm. It is believed that the decline in transmittance is the result not only of absorption of light by oxygen but also of the effects produced by the evolution of ozone. The production of ozone not only causes a decline in transmittance but may also contaminate the surface of optical members, which are used in the projection optical unit, owing to a chemical reaction between ozone and other substances. There is the possibility that such contamination will degrade the exposing capability of the exposure apparatus.
In an exposure apparatus that uses exposing light having an emission spectral line that overlaps the absorption spectrum region of oxygen, as in the manner of the F2 excimer laser, it is known to use an inert gas such as nitrogen to fill the entire optical path of the exposing light in order to avoid the problems of a decline in transmittance and the generation of ozone. Further, the specification of Japanese Patent Application Laid-Open No. 6-20927 describes an exposure apparatus using X rays having properties similar to those of an F2 excimer laser. The exposure apparatus is sealed within a chamber, the interior of the chamber is evacuated and exposure is carried out in such an environment of reduced pressure.
These conventional techniques involve a certain problem. Specifically, the arrangement is such that the entirety of the optical path of the exposing light is sealed within a chamber and the interior of the chamber is filled with inert gas, or such that the interior of the chamber is evacuated to produce an environment of reduced pressure. As a consequence, there is the possibility that the oxygen in the atmosphere outside the chamber will penetrate into the chamber from extremely small gaps.
Furthermore, in a case where the pressure within the chamber differs from atmospheric pressure, there is the possibility that the projected image will be degraded unless the optical characteristics of the projection optics unit are corrected in dependence upon the value of pressure within the chamber accommodating the projection optics.
The present invention has been proposed to solve the aforementioned problems of the prior art and has as its object to provide an exposure apparatus, semiconductor device manufacturing method and manufacturing plant therefor, in which exposure can be carried out under reliably oxygen-free conditions by making the pressure within the chamber higher than the pressure (atmospheric pressure) outside the chamber to prevent atmospheric oxygen outside the chamber from penetrating into the interior thereof, and in which the optimum projected image can be obtained by correcting the optical characteristics of the projection optics unit in accordance with the value of pressure within the chamber.
According to the present invention, the foregoing object is attained by providing an exposure apparatus and semiconductor device manufacturing method having the characterizing features described below.
Specifically, the present invention provides an exposure apparatus having an illuminating optics unit for irradiating a reticle, on which a predetermined pattern has been formed, with exposing light emitted from an exposing light source, a reticle stage on which the reticle is placed, a projection optics unit for projecting the predetermined pattern of the reticle onto a substrate, and a substrate stage on which the substrate is placed, the apparatus comprising at least one chamber for internally accommodating the illuminating optics unit, the reticle stage, the projection optics unit and the substrate stage; first pressure control means for making pressure inside the chamber higher than pressure outside the chamber; and first correction means for correcting optical characteristics of the projection optics unit in accordance with a value of pressure inside the chamber.
In a preferred embodiment of the present invention, the reticle is irradiated with exposing light, which has been emitted by the exposing light source, via the illuminating optics unit, the predetermined pattern that has been formed on the reticle is projected onto the substrate via the projection optics unit to expose the substrate to the pattern, and the exposing light has an optical path the entirety of which is sealed within at least one chamber, the apparatus further comprising second pressure control means for making pressure inside this chamber higher than pressure outside this chamber, and second correction means for correcting optical characteristics of the projection optics unit in accordance with a value of pressure inside this chamber.
The present invention further provides a method of manufacturing a semiconductor device, the method comprising the steps of: placing a group of manufacturing equipment for performing various processes, inclusive of the above-described exposure apparatus, in a plant for manufacturing semiconductor devices; and manufacturing a semiconductor device by a plurality of processes using this group of manufacturing equipment.
The present invention further provides a plant for manufacturing a semiconductor device, comprising: a group of manufacturing equipment for performing various processes, inclusive of the above-described exposure apparatus; a local-area network for interconnecting the group of manufacturing equipment, and a gateway for making it possible to access, from the local-area network, an external network outside the plant, whereby information relating to at least one of the pieces of manufacturing equipment can be communicated by data communication.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.